Gastrointestinal endoscopy, although highly useful, is limited because only the mucosal lining of the intestinal wall is seen. Endoscopic ultrasound provides a method to view tissue beneath the mucosa, but the existing equipment is expensive and difficult to use. We have developed a simpler method of applying ultrasound that uses a probe passed through the biopsy channel of conventional endoscopes. With this new endoscopic echo probe (EEP) we have obtained ultrasound images of normal animal and excised normal and abnormal human gastrointestinal wall and identified areas needing further study. We will pursue further EEP development with 3 types of ultrasound probes designed to investigate specific questions about the gastrointestinal wall. EEP-1: We will refine our current EEP (20 MHz probe) and investigate its use in imaging mucosal gastrointestinal lesions. Nonsteroidal anti-inflammatory drug-induced (NSAID) gastroduodenal injury and peptic ulcer relapse will be studied to determine lesion depth and character. NSAID induced gastric erosions in normal subjects and patients will be followed to determine whether ultrasound characteristics can distinguish which erosions eventually deepen to form ulcers. Duodenal ulcers will be imaged with EEP-l in the healing phase to determine whether there are characteristics of the tissue under the ulcer predicting relapse. EEP-2: Lower frequency probes (10-18 MHz) and a multiples frequency system will be developed to study staging of esophageal and colonic neoplasia which require a deeper penetrating ultrasonic energy than the 20 MHz EEP.l. Neoplastic invasion in esophageal and colonic lesions will be investigated to determine if more accurate nonoperative staging with EEP-2 can contribute to the outcome of therapy. M-mode: We will develop probes that attach to the gut wall, and generate M- mode signals, which shows muscle thickening during contraction and thinning during relaxation. This new methodology will be used to study muscle physiology in animals and humans and provide pathophysiologic insight into gastrointestinal problems associated with abnormal intestinal mobility. Finally, each of these devices as developed, will be studied in vitro and then tested for safety and efficacy in animals. Initial clinical trials will be conducted cc identify specific problems if they exist. Formal clinical trials will follow to establish the value of these devices and to provide new understanding of the important pathophysiologic processes discussed above.